Pete Thomas / ON THE OUTDOORS

Lining up to chase lake's rainbow trout

Bob Caffey is a flooring contractor, but his alter ego reveals a wilder side.

Meet Trout Only.

He's a part-time fishing guide who on this cool gray morning at Diamond Valley Lake requires only five minutes to hook and land a plump and spirited rainbow trout.

Its coloration is flawless: silvery pink sides giving way to speckled green along the back.

The fins are immaculate, the tail broad. These are classic features among the holdover rainbows for which this sprawling Hemet reservoir is steadily gaining notice.

"I've chased holdovers all over: Isabella, Casitas, Cachuma, Piru, Big Bear . . . ," the guide says, while setting lines for another troll. "But the dynamics here make this the premier holdover lake in the southern half of the state, and it keeps getting better."

To be sure, Diamond Valley Lake, though widely known for its trophy-sized largemouth bass, has developed into a unique trout fishery.

Thousands of holdover rainbows -- hatchery-born fish that were stocked in recent years and have since become wild -- thrive in a reservoir 4.5 miles long, two miles wide and nearly 250 feet deep.

Diamond Valley Lake, only 8 years old, is the largest freshwater reservoir in Southern California. Its cool depths enable trout to remain active year-round.

The larger specimens have attained predatory characteristics similar to those of largemouth and striped bass, and from late May through July are often located with those predators, pursuing shad.

"A lot of guys don't realize that these are top-line predators too," Trout Only says, after reeling in another two-pounder.

He and Barry Ogawa, another holdover nut, are practicing for the May 17 Spring Smackdown, a derby open to children and adults, benefiting the Boys & Girls Clubs of the Southwest.

They have invited me along and we have begun the day slow-trolling along the east dam.

They are bemoaning the weather, explaining that holdovers are more aggressive in sunshine with a rippled surface.

We're using nightcrawlers on six-pound-test lines with split-shot weights to keep the worms at about six feet.

Pasadena angler Mitch Marone, fishing solo in an aluminum skiff, greets us with a fresh holdover caught in the southeast corner.

A biker glides across the dam. In the south-shore treetops, a heron falls under attack by ravens. In a nearby cove, a bass angler nets a four-pound largemouth.

Trout Only says the first time he came here all he could catch were bass, while trolling for trout. Largemouth anglers have complained about so many trout attacking their bass lures.

Such are the woes Diamond Valley Lake anglers must endure.

Trout Only's largest trout? Eight pounds, he says, and there have been lots of sevens, sixes and fives.

"But I once lost what I'm sure was a lake record after a 40-minute fight," he adds.

It was a hook-jawed male that flung the lure after "playing dead" alongside the boat, just as Trout Only bent over to scoop his prize with a net.

The lake record is an 11.30-pound rainbow caught in 2005. But my fishing partners scoff, saying that was a hatchery-raised fish grown to that size and landed less than an hour after it was planted.

Hours have passed and we have landed just five trout, all two to three pounds, but we have crossed the lake and are working the west dam. This is where the bigger fish lurk, especially during warmer months.

Surprisingly, the best time to target the larger holdovers is during the summer.

In fact, one sweltering August day, Trout Only and Ogawa were fishing here alone. It was 105 degrees -- catfish weather -- and they had forgotten to put drinks in the cooler.

But they were pulling up hefty rainbows and reluctant to make the long trek back to the marina.

"So we rationed our ice cubes. We were like survivors," Ogawa recalls. "We took turns dipping our towels into the ice water and dabbing our faces. I lost five pounds that day."